8021q: fix a memory leak for VLAN 0 device

8021q: fix a memory leak for VLAN 0 device

commit 78bbb15f2239bc8e663aa20bbe1987c91a0b75f6 upstream.

A vlan device with vid 0 is allow to creat by not able to be fully
cleaned up by unregister_vlan_dev() which checks for vlan_id!=0.

Also, VLAN 0 is probably not a valid number and it is kinda
"reserved" for HW accelerating devices, but it is probably too
late to reject it from creation even if makes sense. Instead,
just remove the check in unregister_vlan_dev().

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Fixes: ad1afb003939 ("vlan_dev: VLAN 0 should be treated as "no vlan tag" (802.1p packet)")
Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: The vlan driver didn't leak memory itself, but might
 cause underlying drivers to leak resources for VID 0.  Keep the check for
 hardware acceleration.]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>